Package org.eclipse.remote.telnet.core

Class TelnetProtocol

java.lang.Object
java.lang.Thread
org.eclipse.remote.telnet.core.TelnetProtocol
All Implemented Interfaces:
Runnable
public class TelnetProtocol extends Thread
This class encapsulates a TELNET connection to a remote server. It processes incoming TELNET protocol data and generates outbound TELNET protocol data. It also manages two sets of TelnetOption objects: one for the local endpoint and one for the remote endpoint.

IMPORTANT: Understanding this code requires understanding the TELNET protocol and TELNET option processing, as defined in the RFCs listed below.

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  • Field Details

    • STATE_INITIAL

      protected static final int STATE_INITIAL
      TELNET connection state: Initial state.
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    • STATE_IAC_RECEIVED

      protected static final int STATE_IAC_RECEIVED
      TELNET connection state: Last byte processed was IAC code. code.
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    • STATE_WILL_RECEIVED

      protected static final int STATE_WILL_RECEIVED
      TELNET connection state: Last byte processed was WILL code. code.
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    • STATE_WONT_RECEIVED

      protected static final int STATE_WONT_RECEIVED
      TELNET connection state: Last byte processed was WONT code.
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    • STATE_DO_RECEIVED

      protected static final int STATE_DO_RECEIVED
      TELNET connection state: Last byte processed was DO code.
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    • STATE_DONT_RECEIVED

      protected static final int STATE_DONT_RECEIVED
      TELNET connection state: Last byte processed was DONT code.
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    • STATE_SUBNEGOTIATION_STARTED

      protected static final int STATE_SUBNEGOTIATION_STARTED
      TELNET connection state: Last byte processed was SB.
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    • STATE_RECEIVING_SUBNEGOTIATION

      protected static final int STATE_RECEIVING_SUBNEGOTIATION
      TELNET connection state: Currently receiving sub-negotiation data.
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    • BUFFER_SIZE

      protected static final int BUFFER_SIZE
      Size of buffer for processing data received from remote endpoint.
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    • rawBytes

      protected ByteBuffer rawBytes
      Holds raw bytes received from the remote endpoint, prior to any TELNET protocol processing.

    • processedBytes

      protected byte[] processedBytes
      Holds incoming network data after the TELNET protocol bytes have been processed and removed.

    • processedStringBuffer

      protected StringBuffer processedStringBuffer
      This field holds a StringBuffer containing text recently received from the remote endpoint (after all TELNET protocol bytes have been processed and removed).

    • telnetState

      protected int telnetState
      Holds the current state of the TELNET protocol processor.

    • remoteIsTelnetServer

      protected boolean remoteIsTelnetServer
      This field is true if the remote endpoint is a TELNET server, false if not. We set this to true if and only if the remote endpoint sends recognizable TELNET protocol data. We do not assume that the remote endpoint is a TELNET server just because it is listening on port 23. This allows us to successfully connect to a TELNET server listening on a port other than 23.

      When this field first changes from false to true, we send all WILL or DO commands to the remote endpoint.

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    • localOptions

      protected org.eclipse.remote.telnet.core.TelnetOption[] localOptions
      An array of TelnetOption objects representing the local endpoint's TELNET options. The array is indexed by the numeric TELNET option code.

    • remoteOptions

      protected org.eclipse.remote.telnet.core.TelnetOption[] remoteOptions
      An array of TelnetOption objects representing the remote endpoint's TELNET options. The array is indexed by the numeric TELNET option code.

    • receivedSubnegotiation

      protected byte[] receivedSubnegotiation
      An array of bytes that holds the TELNET subnegotiation command most recently received from the remote endpoint. This array does _not_ include the leading IAC SB bytes, nor does it include the trailing IAC SE bytes. The first byte of this array is always a TELNET option code.

    • nextSubnegotiationByteIndex

      protected int nextSubnegotiationByteIndex
      This field holds the index into array receivedSubnegotiation of the next unused byte. This is used by method processTelnetProtocol(int) when the state machine is in states STATE_SUBNEGOTIATION_STARTED and STATE_RECEIVING_SUBNEGOTIATION.

    • ignoreSubnegotiation

      protected boolean ignoreSubnegotiation
      This field is true if an error occurs while processing a subnegotiation command.
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    • width

      protected int width
      This field holds the width of the Terminal screen in columns.

    • height

      protected int height
      This field holds the height of the Terminal screen in rows.

    • shell

      protected TelnetCommandShell shell
      This field holds a reference to the TelnetCommandShell.

    • socket

      protected Socket socket
      This method holds the Socket object for the TELNET connection.

    • inputChannel

      protected ReadableByteChannel inputChannel
      This field holds a reference to an ReadableByteChannel object used to receive data from the remote endpoint.

    • serverOutputStream

      protected OutputStream serverOutputStream
      This field holds a reference to an OutputStream object used to send data to the remote endpoint.

    • clientOutputStream

      protected OutputStream clientOutputStream
      This field holds a reference to an OutputStream object used to send data to the client.

    • localEcho

      protected boolean localEcho
      UNDER CONSTRUCTION

    • TELNET_SE

      static final byte TELNET_SE
      Command code: Subnegotiation End.
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    • TELNET_NOP

      static final byte TELNET_NOP
      Command code: No-op.
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    • TELNET_DM

      static final byte TELNET_DM
      Command code: Data Mark.
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    • TELNET_BREAK

      static final byte TELNET_BREAK
      Command code: Break.
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    • TELNET_IP

      static final byte TELNET_IP
      Command code: Interrupt Process.
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    • TELNET_AO

      static final byte TELNET_AO
      Command code: Abort Output.
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    • TELNET_AYT

      static final byte TELNET_AYT
      Command code: Are You There.
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    • TELNET_EC

      static final byte TELNET_EC
      Command code: Erase Character.
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    • TELNET_EL

      static final byte TELNET_EL
      Command code: Erase Line.
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    • TELNET_GA

      static final byte TELNET_GA
      Command code: Go Ahead.
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    • TELNET_SB

      static final byte TELNET_SB
      Command code: Subnegotiation Begin.
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    • TELNET_WILL

      static final byte TELNET_WILL
      Command code: Will.
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    • TELNET_WONT

      static final byte TELNET_WONT
      Command code: Won't.
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    • TELNET_DO

      static final byte TELNET_DO
      Command code: Do.
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    • TELNET_DONT

      static final byte TELNET_DONT
      Command code: Don't.
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    • TELNET_IAC

      static final byte TELNET_IAC
      Command code: Interpret As Command.
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    • TELNET_IS

      static final byte TELNET_IS
      Command code: IS.
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    • TELNET_SEND

      static final byte TELNET_SEND
      Command code: SEND.
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    • TELNET_OPTION_TRANSMIT_BINARY

      static final byte TELNET_OPTION_TRANSMIT_BINARY
      Option code: Transmit Binary option.
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    • TELNET_OPTION_ECHO

      static final byte TELNET_OPTION_ECHO
      Option code: Echo option.
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    • TELNET_OPTION_SUPPRESS_GA

      static final byte TELNET_OPTION_SUPPRESS_GA
      Option code: Suppress Go Ahead option.
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    • TELNET_OPTION_TERMINAL_TYPE

      static final byte TELNET_OPTION_TERMINAL_TYPE
      Option code: Terminal Type
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    • TELNET_OPTION_NAWS

      static final byte TELNET_OPTION_NAWS
      Option code: Negotitate About Window Size (NAWS)
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  • Constructor Details

  • Method Details

    • getOutputStream

      public OutputStream getOutputStream()

    • setClientOutputStream

      public void setClientOutputStream(OutputStream stream)

    • isConnected

      public boolean isConnected()
      Returns true if the TCP connection represented by this object is connected, false otherwise.

    • isRemoteTelnetServer

      public boolean isRemoteTelnetServer()
      Returns true if the TCP connection represented by this object is connected and the remote endpoint is a TELNET server, false otherwise.

    • setTerminalSize

      public void setTerminalSize(int newWidth, int newHeight)
      This method sets the terminal width and height to the supplied values. If either new value differs from the corresponding old value, we initiate a NAWS subnegotiation to inform the remote endpoint of the new terminal size.

    • localEcho

      public boolean localEcho()
      Returns true if local echoing is enabled for this TCP connection, false otherwise.

    • run

      public void run()
      This method runs in its own thread. It reads raw bytes from the TELNET connection socket, processes any TELNET protocol bytes (and removes them), and passes the remaining bytes to a TerminalDisplay object for display.
      Specified by:
      run in interface Runnable
      Overrides:
      run in class Thread

    • initializeOptions

      protected void initializeOptions()
      This method initializes the localOptions[] and remoteOptions[] arrays so that they contain references to TelnetOption objects representing our desired state for each option. The goal is to achieve server-side echoing, suppression of Go Aheads, and to send the local terminal type and size to the remote endpoint.

    • processTelnetProtocol

      protected int processTelnetProtocol(int count)
      Process TELNET protocol data contained in the first count bytes of rawBytes. This function preserves its state between calls, because a multi-byte TELNET command might be split between two (or more) calls to this function. The state is preserved in field telnetState. This function implements an FSA that recognizes TELNET option codes. TELNET option sub-negotiation is delegated to instances of TelnetOption.
      Returns:
      The number of bytes remaining in the buffer after removing all TELNET protocol bytes.

    • telnetServerDetected

      protected void telnetServerDetected()
      This method is called whenever we receive a valid TELNET protocol command from the remote endpoint. When it is called for the first time for this connection, we negotiate all options that we desire to be enabled.

      This method does not negotiate options that we do not desire to be enabled, because all options are initially disabled.